UPDATING IO’S NORTH POLAR GEOLOGIC MAP USING JUNOCAM IMAGES

Williams et al. [1] completed the global geologic mapping of Jupiter’s volcanic moon Io after the conclusion of NASA’s Galileo mission using a set of combined Galileo-Voyager mosaics at 1 km/pixel [2]. The map included a region of poor resolution surrounding Io’s north pole, where detailed mapping was not possible. NASA’s Juno spacecraft, in a polar orbit around Jupiter, has enabled imaging of Io’s north polar region with its JunoCam instrument [3]. Images obtained during flybys in 2023-2024 are enabling us to update the north polar geologic map. Using images from the PJ57 flyby (30 December 2023), we mapped the following features: 1) a darker floor in Vivasvant Patera, and a green floor in Chors Patera indicative of an active lava flow/lava lake whose surface is covered by materials of silicate-sulfur alteration; 2) at least 3 new, small paterae and 5 smaller vents; 3) red, diffuse mantles around the margin of Chors Patera (indicative of venting of at least 4 new mountains, and examples of large blocks that have broken off lineated mountain units and were deposited downslope as part of newly-recognized mottled mountain units; 5) extensive white diffuse halos around several N latitude flow fields, indicative of SO₂ mobilized by the lava surfaces; and 6) multiple white diffuse halos around or near mountains. Although these halos were first recognized in Voyager images [4], we hypothesize that the fractures that form during the mountain building process enable escape of SO₂ from Io’s interior without requiring surface expressions of high temperature volcanic activity.

References: [1] Williams et al., 2011. USGS SIM 3168; [2] Becker & Geissler, 2005. LPSC XXXVI, Abstract #1862; [3] Hansen et al., 2017. Space Sci. Rev., 213, p. 475-506; [4] Smith et al., 1979. Science, 204, 951-972.